An optical detector (or receiver), as is known, is a device which detects the intensity of incident light and provides an electrical signal indicative thereof. Also, an optical modulator (or transmitter) is a device which receives light and provides modulated (or varied) output light by varying an input electrical signal.
Prior art devices do not provide both a detector and a modulator on a single device that also provides bidirectional single fiber optic communications. Instead, two separate fibers must be used to convert an electronic transmit signal to an optical transmit signal, and to convert a received optical signal to an electronic signal.
One common waveguide-integrated optical detector in the art is a leakage-based detector or "evanescent-coupling" detector. In a leakage-based detector, input light is guided along a waveguide (i.e., waveguide layers, having a lower cladding layer and a core layer) located on the device, and a detector layer made of a material having an energy bandgap smaller than that of the energy of the light being detected, is grown adjacent to the core of the waveguide. Light propagating along the waveguide core layer leaks into the detector layer and, because the energy of the light is greater than the bandgap of the detector layer, is absorbed thereby. Such absorption generates electron hole pairs therein which are detected (or collected) by electrodes disposed on the surface of the detection layer, as is known.
However, the leakage-based detector design may not also be integrated with a modulator on the same chip because if electrodes are disposed on the surface of the waveguide core (as is the detector layer) to modulate the light in the waveguide, the electrodes absorb the light in the waveguide, thereby greatly attenuating the light intensity in the waveguide.
Also, requiring a separate device for both receive and transmit precludes bidirectional communications on a single fiber fed directly to the interface chip. Instead, the fiber from the transmitter must be coupled to the fiber from the receiver, requiring more parts and expense.
Thus, it would be desirable to design a combined optical modulator (transmitter) and detector (receiver) on a single chip/substrate (i.e., a transceiver). It would also be desirable to incorporate electronics to control both the modulator and detector on the same chip.